1. Field of the Invention
The present invention relates to a pump circuit, and more particularly, to a pump circuit that can dynamically control a time at which a pump is enabled.
2. Description of the Prior Art
Standard pump circuits consist of a pump, for producing an output voltage; an oscillator, for driving the pump to operate at a certain periodicity; and a limiter, for enabling the oscillator according to the output voltage which is fed back from the pump. When the output voltage becomes too low, the limiter will enable the oscillator to drive the pump. When the output voltage becomes too high, the limiter will disable the oscillator, allowing the output voltage to be reduced once more.
In order for this system to operate correctly, the limiter must be enabled all the time. For certain systems and in certain modes, such as low current modes, this is unnecessary. Instead, a system tries to guess at what time the pump will need to pump, and enables the limiter for these time periods only. This saves power. For an illustration of this kind of system please refer to FIG. 1.
FIG. 1 is a diagram of a conventional pump system 100 that employs an enable controller 140, for enabling the limiter 110. A feedback signal from the pump 130 is input to both the limiter 110 and the enable controller 140. The enable controller 140 then uses this feedback signal as a means of determining when to enable the limiter 110. The enable controller 140 will have a timer built in, and uses a period between the pump output as a means for determining the next time the pump 130 will pump. Such a system, however, is subject to inaccuracies. In many operation modes, the current demand and response time is hard to predict. Furthermore, the output of this system will resemble a sawtooth, as the pump 130 is operational and then bleeds down when it disables. During the bleeding down time, as an output voltage is still generated by the pump 130, the limiter 110 is still enabled and is wasting power.
It is therefore a purpose of the present invention to provide a pump system that can more accurately predict a time at which the limiter needs to be enabled, and can therefore save power.